In the field of photography, a photographer is often confronted with scenes that have extreme imaging properties, such as high dynamic range, unusual color balance, or large variations in contrast. Dynamic range typically refers to a ratio between maximum and minimum values of physical measurement, and in photography specifically refers to a ratio of luminance values. Color balance typically refers to intensities of colors in an image. Contrast is typically determined by the difference in the color and brightness of various objects or different regions within the same view.
In some cases, a scene including extreme imaging properties may have multiple different regions, each with different brightness levels and contrast. For example, a scene might include a first region depicting bright day light and a second region depicting dark shadow. In this situation, the first region depicting bright day light has a different brightness level than the second region depicting dark shadow. Moreover, in such a situation, the level of contrast is high, since the difference in the brightness level of the first region and the brightness level of the second region is large. On the other hand, in a situation where the brightness levels of the multiple different regions are relatively similar, the level of contrast is low, since the difference in the brightness levels is small.
When confronted with a scene having such dramatic variations in contrast, the photographer is often compelled to capture many images of the scene, each with different exposure settings, such as shutter speed. Then in post-capture image processing, the photographer combines the images into an acceptable rendition of the scene, such that an acceptable contrast is achieved. This acceptable rendition may not be achievable due to loss of information during capture that cannot be easily estimated or reconstructed.